Give a pod's containers what a container with its own machine has - #885
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MayCXC wants to merge 10 commits into
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Give a pod's containers what a container with its own machine has#885MayCXC wants to merge 10 commits into
MayCXC wants to merge 10 commits into
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The reaper that runs at a concurrency of one deletes everything in the test directory except the unpacked rootfs it means to preserve. It held that rootfs path as FileManager reports it, under /var, and compared it against the entries of contentsOfDirectory, which reports them under /private/var, so the preserved path never matched any entry and the rootfs was deleted along with the per-test files. The unpack coordinator still held it as unpacked, so the next test opened a rootfs that was no longer there and failed with a missing file error. Resolve both sides with resolvingSymlinksInPathWithPrivate, which exists for this difference between the two views of the same directory.
Tests guarded for Linux are compiled out on macOS, so `make test` reports success without having run them, and nothing says so. The target that does run them is not mentioned anywhere outside the makefile.
The default kernel the tests fetch had drifted from the one users run. container installs kata 3.28.0 and its 6.18.15 kernel, while these tests fetched 3.17.0, so the suite exercised a guest with a different feature set to the one it is meant to represent. Nested runtimes are the visible case: 3.17.0 was built without nf_tables, so a docker daemon inside a container fails there and works on what ships. Kata moved from xz to zstd between those releases, so the archive is no longer named for its compression and tar is left to recognise it rather than being told, which also holds if the format changes again.
A test's rootfs clones, init block, and writable layers land in a directory the runner creates for it and deletes when it finishes, so a test holds disk only while it runs at any concurrency. The run-shared directory holds the unpacked images every bootstrap clones from, and is removed when the run ends.
A container's storage is its rootfs, an optional writable layer, and its mounts; a machine's is its containers' plus the volumes they share. One generic shape describes both the Mount values a machine is configured with and the AttachedFilesystem values it reports once attached, so converting between the two is a map over the structure and the roles cannot drift between configuration and attachment. Device addresses are allocated walking the same sorted order the devices are created in, on both backends. Consumers read roles instead of list positions: the spec builders take a container's mounts without prefix arithmetic, pod volumes mount by name, and a cloud-hypervisor volume's virtiofsd is held by a machine-lifetime reference alongside its containers' reference counts.
Copying a file between the host and a container is reachable only for a container in a machine of its own; the same container placed in a pod has no way to be copied into or out of, so a tool that offers `cp` loses it the moment a container joins a pod. What the transfer needs is the machine, the path the container's filesystem sits at in the guest, and a vsock port, and only the path differs between the two cases. It moves to a type that takes those, which both a standalone container and a pod's containers hand it. The round trip is covered against a running pod, including that a file copied into one container reaches that container alone.
A container with a machine of its own is given the size it asked for plus the guest agent's, so a container that asks for a gibibyte has a gibibyte and the agent runs beside it. A pod hands its size to the machine as it stands, so the agent comes out of what the pod asked for and its containers are left with less: a pod given twelve gibibytes reports eleven and a half. The pod's size and the agent's are added the same way, and what a pod was given is what its containers have.
A container with a machine of its own can be given a block device to write into, with its image mounted read-only beneath, so the image is left as it is and every write lands in the layer. The same container placed in a pod has nowhere to be given one. The layer is attached with the container's other block devices, mounted in the guest as the upper layer of an overlay over the image, dropped from the mounts the runtime spec carries, and unmounted with the container. A pod's containers take one whether they were placed before the machine booted or hotplugged into it afterwards.
The file carried the sibling repository's copyright line, so the license header check found no header it recognized.
Stopping a container tears down what it was running and keeps its place: the name still answers for it, and placing another container under it is refused. Removal is the separate act the runtime specification names for giving the place up, taken once the container has stopped, so a name can run again in a machine that outlives what it last ran. https://github.com/kubernetes/cri-api/blob/master/pkg/apis/runtime/v1/api.proto
This was referenced Aug 27, 2026
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Summary
Five independent fixes for capabilities a container loses the moment it is placed in a pod.
Copying files in and out. Copying a file between the host and a container is reachable only for a container in a machine of its own; the same container placed in a pod has no way to be copied into or out of, so a tool that offers
cploses it the moment a container joins a pod. What the transfer needs is the machine, the path the container's filesystem sits at in the guest, and a vsock port, and only the path differs between the two cases. It moves to a type that takes those, which both a standalone container and a pod's containers hand it.A writable layer. A container with a machine of its own can be given a block device to write into, with its image mounted read-only beneath, so the image is left as it is and every write lands in the layer. The same container placed in a pod has nowhere to be given one. The layer is attached with the container's other block devices, mounted in the guest as the upper layer of an overlay over the image, dropped from the mounts the runtime spec carries, and unmounted with the container. A pod's containers take one whether they were placed before the machine booted or hotplugged into it afterwards.
The machine it asked for. A container with a machine of its own is given the size it asked for plus the guest agent's, so a container that asks for a gibibyte has a gibibyte and the agent runs beside it. A pod hands its size to the machine as it stands, so the agent comes out of what the pod asked for and its containers are left with less: a pod given twelve gibibytes reports eleven and a half. The pod's size and the agent's are added the same way now, and what a pod was given is what its containers have.
Giving a container's place back. Stopping a container tears down what it was running and keeps its place: the name still answers for it, and placing another container under it is refused. Removal is the separate act the runtime specification names for giving the place up, taken once the container has stopped, so a name can run again in a machine that outlives what it last ran. https://github.com/kubernetes/cri-api/blob/master/pkg/apis/runtime/v1/api.proto
A wrong copyright line.
GuestFileTransfer.swiftcarried the sibling repository's line, so the license header check found no header it recognized.Dependency and Merge Order
This targets stock
apple/containerization:mainand depends on #872, which in turn depends on #863. Merge order: #863, then #872, then this. The head carries both prerequisites' commits because all three target stockmain; after they merge, this branch takes currentmainand its remaining diff is the five fixes.Motivation and Context
Discussion: #879. Nothing here touches the swap work in #877, and the five commits are independent of one another, so any can be dropped without the others.
Testing
make containerizationandmake checkclean.swift test: 593 tests in 81 suites passed.make integration: thecpround trip is covered against a running pod, including that a file copied into one container reaches that container alone.Type of Change